107a60dd71
The latest MegaRAID Firmware (for Invader series) has support for 64bit DMA for both streaming and consistent DMA buffers. All Ventura series controller FW always support 64 bit consistent DMA. Also, on a few architectures 32bit DMA is not supported. Current driver always prefers 32bit for consistent DMA and 64bit for streaming DMA. This behavior was unintentional and carried forwarded from legacy controller FW. Need to enhance the driver to support 64bit consistent DMA buffers based on the firmware capability. Below is the DMA setting strategy in driver with this patch. For Ventura series, always try to set 64bit DMA mask. If it fails fall back to 32bit DMA mask. For Invader series and earlier generation controllers, first try to set to 32bit consistent DMA mask irrespective of FW capability. This is needed to ensure firmware downgrades do not break. If 32bit DMA setting fails, check FW capability and try seting to 64bit DMA mask. There are certain restrictions in the hardware for having all sense buffers and all reply descriptors to be in the same 4GB memory region. This limitation is h/w dependent and can not be changed in firmware. This limitation needs to be taken care in driver while allocating the buffers. There was a discussion regarding this - find details at below link. https://www.spinics.net/lists/linux-scsi/msg108251.html Signed-off-by: Kashyap Desai <kashyap.desai@broadcom.com> Signed-off-by: Shivasharan S <shivasharan.srikanteshwara@broadcom.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> |
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README
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.